Cavityless casting mold and method of making same



A ril 15, 1958 H. F. SHROYER 2,830,343

CAVITYLESS CASTING MOLD AND METHOD OF MAKING SAME Filed April 26, 1956 I 5 Sheets-Sheet 1 Jllnrill "MIMI $1 II i MW \\\k k .94 Tlg 3 JNVEN TOR. Harold fifirg/a April '15, 1958 H. F. SHROYER CAVITYLESS CASTING MOLD AND METHOD OF MAKING SAME Filed April 26, 1956 3 Sheets-Sheet 2 I v w.

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JNVENTOR. Hamid Ffiryer BY H. F. SHROYER 2,830,343

3 Sheets-Sheet 3 WWW y INVENTOR. J6me? EASE/'96? April 15, 1958 CAVITYLESS CASTING MOLD AND METHOD OF MAKING SAME FiledApril 26, 1956 area 2,830,343 E Patented A111- 1-958 :2,sse,s4s CAVITYLESS CASTINGNIOLD AND NI ETHOD F G SAN E Harold F. Shroyen Mystic, Conn.

Application Aprii 26, 1956, Serial No. 580,885

5 il'aims. (Cl. 224 196) This invention relates to molds for castings and to a method of making such molds.

While conventional molds with their cavities, formed with the aid of patterns and cores, permit the casting -'of structures of many different configurations, they do not lend themselves readily, if at all, to the casting of structures of "many other desirable configurations, which Would require excessive, if not practically impossible, coring or complicated parting lines, or both. Thus, in

order to lay out-structures intended for -casting,the deby not only permitting expeditious and advantageous casting of many structures not cast heretofore because involving excessive coring or complicated parting of molds therefor, but also affording designers far greater'freedom in laying out structures to-be-cast with first, if not sole,

, consideration for their optimum utility and with little regard to their molding.

It is another important object of the present invention to provide a mold which is devoid of a conventional mold cavity and, instead, has an embedded form which in shape is an exact replica ofthe intended casting to the inclusion of any and all recesses, apertures and other surface configurationswhich heretofore required coring, and which is'accessible'througha conventional gate to a'poured casting charge that causes fairly rapid combustion of the form without leaving appreciable, if any, residue and, hence-,'replaees' the embedded forrn in the mold and solidi- 'fies therein in'toth'e intended-casting of the exact-shape of thereplaced-and vanished form, thereby achieving not only fhe aforementioned coreless molding for castings of most any configuration, :but-alsosiin-ple parting er the moldwith'out any special :regard to the shape of the form.

FIt is a further important object of the present inventiontoideviseta method'of preparingmolds of the aforementioned coreless type with their embedded combustible aforms far more expeditiously and with far less skill than imolds with: conventional cavities,thereby achieving'a "sub- *stantial reduction inrthe cost of many molding operations. Alnother importantobject .of the present invention is withstand rany and all "stresses induced by ordinary hand or power ramming of molding sand thereagainst, but

whichmay also be shaped easier and far more expeditiousany desire d'confi'g'urations 'by conventional'hand or machine shaping and, whenever more convenient, may be made of any number of separate preformed parts that may readily be secured to :each other with adequatefirmness by simple cementing, doweling or wiring, for instance, thereby not only obtaining these iform parts advantageously by expediencies which may be similar, but generally simpler to perform, than those practiced in conventional pattern making, but also :greatly enhancing the simplicity of the aforementioned "molding method not only by permitting the placement-ofnnost:forrn parts, in their entirety and regardlessof :their shapes, fin fl'asks without regard to partinglines, and eliminating the heretofore imperative and tedious tasks of removing impressed patterns :from the molds and frequently-finishing the exposed mold cavities including the placement and fitting of cores therein, but also permitting conventional ramming of molding sand, or an equivalent medium, against the form parts in the molds more expeditiously and with less care than heretoforewith'out impairing the accurate casting reproduction capacityof the molds,

A further object of the present invention is to fabricate the aforementioned form parts for the instant cor'eless molds from suitable materials'which not only have all the aforementionedproperties, but :which are also readily moldable into any specific shape, or extrudableas continuous stock of any desired cross section, therby further facilitatingand 'expeditingthe fabrication of these form parts so much so as :to adapt them for advantageous mass-production molding for many castings-atno greater cosh-and in many cases-at considerablylower cost, than that of conventional cavity rnolding and 'coring 'for the same castings.

:It is another object of thelpresent inv-ention to fabricate the aforementioned form parts of the instant =c'orelessrmolds from relatively inexpensive expanded plastics, :such as polystyrene "or polyethylene, for instance, which may conveniently-be shipped'to 'an'ds'to'cke'd in' foundries in non-expanded form-in containers or :drums of small bulk, and which may be expanded underheat -into lightweight blocks or other shapes of many "times their original volume whenever needed for the fabrication of form par-ts v therefrom, or may 'betexpanded in molds for their direct formation :into such form parts o'r separate elements thereof, thereby not'only eliminating the need "for stocking the various seasoned and r'e'l'atively expensive woods customarily used in pattern and core making, 'but also making itientirely feasible-and economical to pre- Ypare molds for the casting of exceptionally large nonrepeat structures which heretofore involved prohibitive costs of the Wooden patterns and the cores therefor, or which "were formed in :articulatedfashion rather than cast time to the prohibitive molding cost thereof.

Other objects and advantages will appear "to those skilled in the art from the following, considered inconjunction with the-accompanying drawings.

Inthe accompanying drawings, in which certain modes of carrying out the present invention 'are shown for illustrative purposes:

embodying the present invention;

"Iy than conventional pattern materialsand given-most Fig. 1' is'a perspective view of a casting made in a-mold Fig. 2 is a perspective view of a form part used in a "moldfor producing the casting :of :Fig 1 in accordance 'as taken-on the line 4-4ofFig. 3;

Fig. 5 is alongitudinal section through "a part of a mold being vprepared in accordance with the;,='present invention for the exemplary casting of Fig. 1;

fig. -6 is alongitudinal section through the completed mold for the same exemplary casting; and

Referring to the drawings, and more particularly to Fig. 1 thereof, the reference numeral it) designates an exemplary casting which is produced in a mold, and according toa method, embodying the present invention. The exemplary casting It) has presently abo'ttom wall 12, an upwardly extending peripheral rim 14 with a slot 16 in one corner and a hole 18 in one end, and an upwardly extending boss on. the bottom wall 12. Extending upwardly from the bottom wall 12 and inwardly from the opposite sides of the rim 14 are lobes 22, while a strap-like formation 24 is provided on the outside of one of the sides of the rim 14. Furthermore, the boss 20 is slotted at 26 over part of its axial extent, and the strap formation 24 is also slotted as at 28. The ex emplary configuration of the casting 10 has been chosen because it serves well for readily expounding the various significant aspects of the new molding technique employed in the production of castings.

Most significantly, and in accordance with the present invention, the exemplary casting 10 is, first of all, produced in a mold which is devoid of the usual mold cavity and usual insertedcore or cores and, instead, holds a form which in shape an size is exactly identical with the intended casting, save for shrinkage of the latter on solidification, and includes all recesses, apertures and other portions of the intended casting which heretofore required a separate score or cores. This featured form is adapted to be displaced in a mold by a poured casting charge in a manner described hereinafter. Thus, the form for the exemplary casting 10 is shown in perspective in Fig. 2 and designated by the reference numeral 30, it being noted that the form is in all respectsidentical with the casting 10 and its, various parts are identified by the same reference numerals as their identical counterparts of thecasting, except that the with; is added thereto. s

The form is adapted to be displaced in a mold by a pouredcasting charge by being converted substantially 111 its entiretly into a gaseous state and permitted to escape from the mold through suitable'vent provisions. Thus, the form 30 is to this end made of any suitable materral which is readily. combustible substantially without resldue on subjection to a molten casting charge, and which is sufficiently rigid safely to withstand the stresses lnduced by the customaryramming of molding sand thereagainst. A tested material suitable for-this purpose is a certain plastic in an expanded state, namely, polystyrene. used for making, entirely. satisfactory forms for various castings, among them a form of the configuration shown Thus, polystyrenejn an expanded state has been in Fig. 2 for producing an entirely satisfactory aluminum casting of the configuration shown in Fig. 1. With respect to the use of this expanded plasticfor making these forms, it has been found that it is well adapted for the intended purpose if it. is expanded to a density of substantially not much more, and. preferably less than 2 lbs. per cubic foot, for if. this material has substantially greater density ,it will not readily burn away on subection to. a molten casting charge.v On the other hand, there is a limit to the expansion of this material in order to be suitable for forms of this type, for if its density becomes too low it maylack adequate strengthto withstand ordinary molding pressures and other stresses and give way thereunder, at least in part sufficiently to spoil a mold. t I

The polystyrene used experimentally may be purchased on the market either in a non-expanded state in convenient containers or drums, or in an expanded state 1n the form of blocks, sheets and bars. Expanded polystyrene may also be extruded as continuous bar stock of most any profile or cross-sectional shape, the expansion and shaping of the stock customarily taking place on leaving the extrusion die. In either case, the usual granule-like non-expanded polystyrene particles are, on

subjection to heat, expanded and formed into solid bodies of many times the volumes of the nonexpanded particles from which they were formed by expansion. Non- .expanded polystyrene may also be expanded into any desired singular shape by being heated and compressed in a mold. Finally, polystyrene in expanded form may readily be shaped by most conventional hand or machine operations.

With the aforementioned variousexpediencies available for forming expanded polystyrene into most any shape, it is comparatively easy to make a form of this material for the production of a casting of most any configuration. Thus, insofar as the exemplary form 30 (Fig. 2) is concerned, the same may, instead of being shaped from a solid block of expanded polystyrene in a laborious and expensive fashion, be advantageously formed of several simple parts which may be joined in any suitable manner, as by simple cementing, doweling or wiring, for instance. In the present example, the bottom wall 12' of the form 30 may be cut and shaped from a suitable block of expanded polystyrene, and the rim 14' may similarly be cut and shaped from a suitable block of the same material, the slot 16 and hole 18 being provided therein by suitable hand or machine operations. Thus, the slot 16 may readily be cut with a suitable knife, while the hole 18 is advantageously drilled. After forming the parts 12' and 14, they may be secured to each other in their proper relationship by cementing them together as at 32, the cement layer between these parts as well as the other parts of the form 30 being shown in Figs. 2 to 4 of exaggerated thickness for clearness of illustration. The boss 20" may next be cut from suitable expanded polystyrene bar stock, and slotted at 26' in any suitable manner as with a knife or milling tool, whereupon this boss may in its proper location on the bottom wall 12 be cemented thereto as at 34. The lobes 22 may then be cut from a suitable block 'of expanded polystyrene and shaped by hand or by a machine operation .or operations, whereupon they may in their proper locations on the bottom Wall 12' and rim 14 be cemented thereto as at 36. Finally, the strap formation 24' may be cut from a suitable block of expanded polystyrene and shaped, as well as slotted at 28', by hand or by machine operations, and then cemented to the bottom wall 12 and rim 14 as at 38.

While the described form 30 has been described as being made of expanded polystyrene, it is, of course, fully within the purview of the present invention to use any other material which is suitable for this purpose, as long as it is readily combustible substantially without residue on subjection to a molten casting charge, and may readily be shaped by hand or machine operations. Also, while in the above described exemplary formation of the form 39 (Figs. 2 to 4) the various parts thereof are cemented together, they may just as readily be wired together or in part doweled together.

substantial, residue, and several such cements are available on the market. Furthermore, if the casting 10 is to be produced in quanity, it may well be advantageous,

[from the viewpoint of expeditiousness and cost, to make a mold, or several molds, in which to expand polystyrene directly into as nearly the overall configuration of the form 30 as molding will permit, and to have recourse to further molds or extruded profile stock to obtain the missing part or parts of the molded form for their ready attachment 'to the latter. It is thus obvious from the foregoing that various expediencies for making forms for various castings may be chosen from for optimum economy of any given casting operation or operations, keeping in mind that forms of the present type eliminate all conventional coringfor castings ofany surface configuration, as will appear more obvious hereinafter.

Of course, whenever parts of a 1 combustible form are cemented together, the cement used a for this purpose should burn without leaving any, or any assas in Reference is now had tofFigs. i" to '8; which. not only show a mold 40 oflthe. instant cavitylesstype. but. also illustrate the'technique or method'involved.inpreparing this mold. More particularly, the exemplary. mold'shown is formed for the production ofthe. exemplary. casting 10 (Fig. 1) and; hence, includes. the form,30."(Fig. 2,)-.. In preparing the mold, a conventional. flask 42jinay in inverted fashion be placedon. a molding'board 444mg, and the form 30' is also placed on the same board. Within the confines 'of' the flask,,pre.ferably. with its. bottomwall 12 lowermost. The flask 4.2 is. then gradually. filledt with molding sand S which is intermittently rammed, by hand or power. operation, throughout the, flask andalso. against the form 3d, care being takenthat; sandi-s rammed into and'fills all: the recesses inthe form, namely,'the hole 18 and the slots 16; 26'and 28, the'respective sand fillings 4.6, 48, 50 and 52 therein. (Figs, 5. to 8). constituting in fact cores which, in distinct contrast-to, conventional-prefabricated. and inserted cores, are. formed, notonly by: the

same molding sand ofjwhich the compactedmoldbodyt is formed, but simultaneously'with;the compactingof. the latter. Thus, the instant cores are. not. only. integral parts of the moldbody B, buttheyalso interlock with the form 3'0 so. that the. latter cannot; be removed; from. the

mold body without destroyingthe same;

Having completed the formation and, compacting of the mold body B in the flask 42 and-overall. bedding of the form 30 therein, the. flask isremovedfrom the board M'andplaced onthe floor or any. other. support, this time with its. top up, whereupon a. conventional; cope-5 L is placed on top of. the flask, the former: being lo ated; on

the latter by suitable'pilot pins 56 which are. receivedin ears 5%: (Fig. 6).. Afterapplying. a suitable, separator,

usually a powder, to the, top planeof themoldbody- B in the flask, the superposed. cope. 541' is. gradually filled with the same molding. sand S} which iS.inter-mittently rammed into the moldv body 13.. The. cone; 54'is.,also suitably gated and rifsered at .60; and '62, Yrespectiyely;,the

gate do which may be of entirely conventional cross-sectional dim nsions, being at thetop prefer-ably. enlarged into a splash basin 64. which may alsobeof entirely conventional dimensions, and the riser 62, which may also be of entirely. conventional. cross-sectional dimensions, may be similarly enlargedat. the topdfso desired.

The cope54. isthenremoved-from; the flask 42, whereupon a multiplicity ofvents 6.8- 31163 formed in the mold body B in the cope by repeatedly poking thereinto, an i'cepick-like tool-which maybeof the thickness of an ordinary icepick, for example. In the present example, in which the form 30 is made of expanded polystyrene that requires atmospheric air for its combustion, vents are also driven into the form 30 in the flask, especially where the form is locally more bulky than in other places, in order to admit to the form adequate atmospheric air for its combustion on subjection to a molten casting charge. Of course, the vents serve also as exhaust passages for the products of combustion of the form. For convenience of illustration, the vents which extend into the interior of the form 30 in the flask 42 are shown in Figs. 6 and 7 as extensions of vents 68 in the cope 54, while they are in reality offset from each other at the partition of the mold bodies B and B. Other vents confined to the cope are indicated at 68. Next, a relatively shallow runner 66 of accustomed dimensions may be formed in the mold body B in the flask 42 for communication between the gate 60 and the embedded form 30, the runner 66 being advantageous for subsequently breaking the cast gate from the casting proper without breaking out part of the rim 14 of the latter, as will be readily understood. For the same reason, the riser 62, while shown extending from within the confines of the embedded form 30, may preferably be arranged outside thereof and connected with the form through a shallow runner similar to the formed, the cope 54 is again placed on top of the flask 42.

- castingv has. solidified. in the. mold,. it may be knocked therefrom. in. the. conventional manner, thecast gate. and riser. being broken. from the, casting byl a hammer blow or blows, Preferably beforethe. casting is knocked from the. mold. The. casting; thusformed. (Fig. 1.). has truly reproduced not only the. hole- 18,. and. the slots 1:65,, 26' andZST of the form. 30, butall other, surfaceconfigurations thereof even to the: finest details (Fig; 2.).

While in the exemplary mold 40 of Figs. 6 to 8. the gate 60an'd riser 62 are provided separately from the'form 3Q,,-it.is,. of. course, entirelyfeasible to provide the. gate andriser, as integral. partsofthe f0rm.30, inwhich case the. cope. 54 need. not, beremoved from the-flask, 42 for cutting the runner 66.

It.f.ollows from the preceding. that a-mold: of the instant cavityless type and with an embedded. combustible form of. the exact shape of an intendedcasting, to .the. inclusion of any and all recesses, apertures and other. surface; confi'gu'rations thereof, readily lendsoitselfto the castingv of structures. of. many desirable. configurations which..he11etofore. required. excessive, if not, practically. impossible, coding; or Partinglines, or both. .While it. is abundantly clear. fromthe. foregoing. that a. mold of the; instant. cavityless type requires no separate CO1TlI1g .I'.6g3I(llfiSSOfthfi configuration, of an'intended casting, it is..also,cle.ar that partinglinesmay' be. ignored, and; that there isno. parting problem,;f.o1'. molding fon any casting in accordance. with the. present molding. methodor. technique... Thus, insofar 'as parting. is. concerned. in. connection with: the. instant 'leading a gate and-ari'ser as wellasamultiplicity ofvents to the wholl'y embedded form, and thus eliminating the need for thecopes tz Also, whileit is; true that in mold- 'ing -according tothe present method a combustible form is required for the production of each casting, the overall cost of any particular molding operation done in accordance with the present method may, despite the cost of the combustible forms, be nevertheless far more economical than if done in accordance with the heretofore conventional techniques. Thus, the cost of the combustible forms may be far less than the cost of conventional coring alone in the case of many castings. Also, the preparation of a mold of the instant cavityless type is far more expeditious and requires far less skill than the preparation of a mold with a conventional cavity, for reasons stated here inoefore, thereby achieving a further reduction in the cost of many molding operations. Also, expanded plastic, such as polystyrene, is much less expensive than the various woods from which conventional patterns are made, thus indicating the advantageous fabrication of a form from such combustible material for the casting of an extra large non-repeat structure which most likely would be formed in an articulated fashion rather than simply cast in a conventional manner due to prohibitive pattern cost and perhaps also coring cost. Finally, the instant combustible forms need not necessarily be replicas of entire castings to be produced, but they may also be used as form. inserts in conventional cavity molds as extensions of the mold cavitiesin places where recourse to conventional coring would otherwise be necessary. For example, a'conventional mold with a cavity of the shape of the casting 10, modified to the extent of lacking the hole 18 and the slots 16 and 26, may be provided, and the slotted strap formation 24 of the casting may be provided for in the mold by a combustible form insert of the exact configuration of this strap formation which is embedded in the molding sand and exposed to the mold cavity where it will, when cast, merge into the rim 14 of the produced casting.

A mold of the instant cavityless type lends itself, of course, to the casting of structures in all metals'in which castings may be produced in conventional cavity molds. Thus, by way of example, a mold of the instant type lends itself to the casting of structures in gray iron, white iron, steel, bronze, brass and aluminum, among others. In fact, a mold of the instant cavityless type has proved advantageous in casting white'iron, in that it received and satisfactorily cast a charge of the latter as it was taken directly from an electric furnace, whereas white iron has to be cooled for some time after leaving an electric furnace before it may be poured into a conventional'cavity mold without ruining the same or producing a spoiled casting.

While in the foregoing description the mold bodies B and B have been described as being formed of molding sand, they may, of course, be formed of any other suitable molding material, such as plaster of Paris, readily flowing cold-set sand mixtures and the sand mix used for CO setting, for instance.

The invention may be carried out in other specific ways than those herein set forth without departing from the spirit and essential characteristics of the invention, and the present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range'of the appended claims are intended to be embraced therein.

What is claimed is:

1. A method of casting, comprising the steps of embedding in a mold body a form combustible substantially without residue on subjection to a molten casting charge and shaped for exact reproduction as a casting, providing in said mold body a passage for a molten casting charge to said embedded form, and pouring into said passage a molten casting charge for burning and replacing said embedded form in said mold body.

2. A method of casting, comprising the steps of embedding in a mold body a form having a recess and being combustible substantially without residue on subjection to a molten casting charge and shaped for exact reproduction as a casting including said recess therein, with part of said mold body filling said recess in said form and interlocking said mold body and form against removal of the latter from the former, providing in said mold body a passage for a molten casting charge to said embedded form, and pouring into said passage a molten casting charge for burning and replacing said embedded form in said mold body.

3. A method of casting, comprising the steps of wholly embedding in a mold body a form combustible substantially without residue on subjection to a molten casting charge and shaped for exact reproduction as a casting, forming in said mold body a gate and a multiplicity of spaced vent passages leading to said embedded form and pouring into said gate a molten casting charge for burning and replacing said embedded form in said mold body.

4. A method of casting, comprising the steps of wholly embedding in a mold body a form combustible substantially without residue on subjection to a molten casting charge and shaped for exact reproduction as a casting, forming in said mold body a gate and a multiplicity of spaced vent passages leading to said embedded form of which at least part of said vent passages are extended into the interior of said form, and pouring into said gate a molten casting charge for burning and replacing said i embedded form in said mold body.

5. A method of casting, comprising the steps of wholly embedding a form, having a recess and being substantially without residue on subjection to a molten casting charge and shaped for exact reproduction as a casting including said recess therein, in a body of molding sand and rammingthe latter against said form and into said recess therein to fill the datterand interlock therewith against removal of said form from said sand body, forming in said rammed sand body a gate and a multiplicity of spaced vent passages leading to said form, and pouring into said gate a molten casting charge for burning and replacing said embedded form in said sand body.

References Cited in the file of this patent UNITED STATES PATENTS 1,758,380 Spiro May 13, 1930 2,583,533 Hiensch Jan. 29, 1952 2,628,394 Valyi Feb. 17, 1953 FOREIGN PATENTS 646,804 Great Britain Nov. 29, 1950 

1. A METHOD OF CASTING, COMPRISING THE STEPS OF EMBEDDING IN A MOLD BODY A FORM COMBUSTIBLE SUBSTANTIALLY WITHOUT RESIDUE ON SUBJECTION TO A MOLTEN CASTING CHARGE AND SHAPED FOR EXACT REPRODUCTION AS A CASTING, PROVIDING IN SAID MOLD BODY A PASSAGE FOR A MOLTEN CASTING CHARGE TO SAID EMBEDDED FORM, AND POURING INTO SAID PASSAGE A MOLTEN CASTING CHARGE FOR BURNING THE REPLACING SAID EMBEDDED FORM IN SAID MOLD BODY. 